parsec

par·sec

a unit of distance, usually used to measure the distance to a star, equal to 206,265 astronomical units (3.0857 x 10 kilometers or 1.92 x 10 miles or 3.2616 light years): it is the distance at which an angle of 0° 0? 1? (one second of arc) would form a triangle having an opposite side with a length of one astronomical unit: abbrev. pc

A unit of astronomical length equal to 3.26 light-years. It is based on the distance from Earth at which a star would have a parallax of one second of arc. Its metric equivalent is about 30.8 trillion km (19.1 trillion mi). It is used in measuring distances in interstellar and intergalactic space. The closest star to Earth, Alpha Centauri, is about 1.3 parsecs away.